Rotary pump and motor hydraulic transmission system



5 Sheets-Sheet 1 n T. N oc o ucoo n W. FERRIS ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION SYSTEM Filed Feb. 5, 1945 Aug. 2, 1949.

lNVENTOR WALTER FERRIS B Zuzana AT TORNEY Aug. 2, 1949. 2,477,974

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION SYSTEM w. FERRIS 5 Sheets-Sheet 2 Filed Feb. 5, 1945 INVENT OR WALTER FERRIS BY W WTTORNEY W. FERRIS Aug. 2, 1949.

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION SYSTEM Filed Feb. 5; 1945 5 Sheets-Sheet 3 Constant speed motor Slip clutch i 18 Different 0! FIG. '3

INVENTQR WALTE R FERRIS BY 2/ WATTORNEY Aug. 2, 1949. w. FERRIS 2,477,974

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION SYSTEM Filed Feb. 5, 1945 5 Sheets-Sheet 4 FIG. 4

- WALTER' FERRIS BY h I 5 Airman INVENTOR v 5 Shegts-Sheet 5 INVENTOR BY I ATTORNEY W. FERRIS ms s o Z. 6 Oh h AHw EHQM 3M m 8. mm

ROTARY PUMP AND MOTOR HYDRAULIC TRANSMISSION SYSTEM Aug. 2, 1949.

Filed Feb. 5, 1945 Patented Aug. 2, 1949 ROTARY PUMP AND MOTOR masonic TRANSMISSION SYSTEM Walter Ferris, Milwaukee, Wis., assignor to The Oilgear Company, Milwaukee, Wis., a corporation of Wisconsin Application February 5, 1945, Serial No. 576,243

20 Claims.

This invention relates to hydraulic drives of the type having a hydraulic motor for driving a machine or other apparatus, a pump for supplying motive liquid to the motor to energize it, and a control for varying the relative displacements of the pump and the motor to thereby control the speed of the motor.

A drive embodying the invention is particularly adapted for driving the lighting and air conditioning apparatus .of a railway car and it will be explained in connection therewith but it is to be understood that the invention may be employed for other purposes. I

The power for driving the lighting and air conditioning apparatus of a railway car is ordinarily derived from the car axle which rotates in one direction or the other at varying speeds in ac cordance with the direction and speed of the car movement and which moves angularly and vertically in respect to the car body as the car passes around curves and over: uneven portions of the track.

A pump ordinarily discharges liquid in a direction and at a rate dependent upon the direction and rate at which it is driven and a hydraulic motor ordinarily operates in a direction and at a speed dependent upon the direction and rate of flow of the liquid which energizes it so that, if the pump were driven from the car axle, the motor would ordinarily operate in opposite directions alternately and at varying speeds but the car lighting and air conditioning apparatus must always be driven in the same direction and at a substantially constant speed.

The present invention has as an object to provide a hydraulic drive including a pump which will deliver liquid in but one direction regardless of the direction in which it is driven.

Another object is to provide a hydraulic drive having a pump which will maintain its displacement at a given maximum at low speeds and will automatically vary its displacement in response to variations in speed above a given speed.

Another object is to provide a hydraulic drive in which a pump and a motor are connected by fluid channels which permit the pump to move relatively to the motor.

Another object is to provide a hydraulic drive having a pump driven at varying speeds, a motor energized by the pump and means for preventing the motor speed from exceeding a predetermined maximum regardless of the pump speed.

Another object is to provide a hydraulic 'drive including a pump which may be supported from and driven by an axle of a railway car, a hydraulic I motor for driving the lighting and air conditioning apparatus of the car, and a control for maintaining the motor speed constant after it reaches a predetermined maximum.

These and other objects and advantages will 2 appear from the description hereinafter given of a hydraulic drive in which the invention is embodied.

According to the invention in its general aspect and as applied to a railway car, the lighting and air conditioning apparatus of the car is driven by a hydraulic motor through an overrunning clutch, the motor is energized by liquid supplied thereto from a reversible variable displacement pump which is supported from and driven by an axle of the car, the reversing mechanism of the pump is operated in response to reversal of car movement so that the pump always delivers liquid in the same direction, the displacement varying mechanism of the pump is operated in response to variations in car speed above an intermediate speed, and the motor speed is maintained constant after it reaches a predetermined maximum.

The invention is exemplified by the hydraulic drive shown schematically in the accompanying drawings in which the views are as follows:

Fig. 1 is a side view partly in section of portions of a railway car having a compartment suspended from the car body and its lighting and air conditioning apparatus (not shown) arranged within the compartment according to the usual practice and driven by a hydraulic drive which is constructed according to the invention.

Fig. 2 is a plan view taken substantially in the plane indicated by the arrows 2-2 on Fig. l but with the truck frame omitted except for small portions thereof adjacent the journal boxes.

Fig. 3 is a diagrammatic view illustrating the control for the motor which drives the car lighting and airconditioning apparatus.

Fig. 4 is a diagrammatic view illustrating the control for the pump which supplies liquid for energizing the motor shown in Figs. 1 and 3.

Fig. 51s a diagram of the hydraulic circuit.

Since air conditioned railway cars are well known, only so much of the car has been illustrated as is necessary to show the application of the invention thereto. As shown in Fig. 1, the car has a compartment l suspended from the car body 2 and enclosing a hydraulic motor 3 which is adapted to drive the car lighting and air conditioning apparatus not shown.

The car lighting and air conditioning apparatus is assumed to include an air conditioner, an A. C. motor-generator and a D. C. motor-generator. When the A. C. motor-generator is driven, it supplies current for lighting the car and, when it is energized by current from a source outside the car, it drives the D. C. motor-generator and the air conditioner. When the D. C. motor-generator is driven, it supplies current for charging the car batteries and, when it is energized by current from the batteries, it drives the A. C. motor-generator and the air conditioner. In

erators, it is connected thereto through an overrunning clutch 4.

Car body 2 is pivotally supported in the usual manner upon a pair of trucks each of which has a pair of wheels arranged at each end thereof to support the car upon the track but only a portion of one truck has been shown as the car per se forms no part of the present invention.

In the portion shown, a pair of wheels 5 is supported upon a track 6 and fixed upon an axle I having opposite ends thereof mounted in a pair of journal boxes 8 which are slidable vertically in opposite sides of the frame 9 of the truck and support car body 2 through springs as is well known.

Hydraulic motor 3 is adapted to be energized by liquid supplied thereto from a reversible variable displacement pump ill which is arranged beneath the car body 2 and connected to axle I by a suitable drive i I so that pump I is driven in one direction or the other in response to movement of the car in one direction or the other.

Pump I0 is fixed to a rigid crossbeam H which has a pair of arms l fixed to its opposite ends and extending from one side thereof as shown in Figs. 1 and 2. The two arms l5 are connected,

respectively, to two lugs I6 which are welded or otherwise rigidly secured, respectively, to the two journal boxes 8 and support crossbeam M at one side thereof. The other side of crossbeam l4 may be suspended by a hangar which is connected directly thereto but, with the type of pump shown, it is preferably connected to a housing ll which encloses the control mechanism for pump l0. Housing I1 is fixed to or formed integral with a housing l8 which encloses pump Ill and is fixed to crossbeam l4 so that housings l1 and I8 and crossbeam l4 form a rigid support for pump I0.

As shown in Figs. 1 and 2, the hanger for the pump support may include a curved track such as an I-beam I9 which is fixed by an upper flange to the center sill of the car body, a trolley 2| which is mounted upon the lower flange of track I9 and a link 22 which is pivotally connected to trolley 2| and to suitable lugs 23 fixed to housing II from the centerline of the pump support.

When the car passes around a curve, the truck will pivot beneath the car body and trolley 2| will move along the track l9 so that hanger 2 l-22 remains substantially vertical at all times. In order to prevent the pump support from dropping upon track 6 in case hanger 2I-22 should fail, a link 24 has its lower end pivoted to housing l8 and its upper end slotted to receive a pin 25 carried by truck frame 9.

order that the pump support may pivot relativelyto axle 1 and to permit adjustment of drive H, the two arms l5 are pivotally connected, respectively, to the two lugs l6 by two eccentric pins 26 each of which has attached thereto a lever 21 by means of which it may be rotated to move the pump support toward or from axle 1.

The arrangement is such that the pump 9- port may pivot upon pins 26 in response to vertical movements of car body 2 relative to axle I while eccentric pins 26 positively retain the pump support in parallelism with axle 1 and, since hanger 2l -22 is connected to the pump support at a single point upon the centerline thereof and its upper end is movable transversely of car body 2 so that the pump support cannot be moved laterally or tilted by movement of car body 2, no material distortion of drive II will occur.

In order that drive ll may be properly lubricated and be protected from dust and other foreign matter, it is preferably enclosed within a suitable enclosure including a housing 28, which is rotatably supported upon axle I, and a flexible and extensible shield 29 which connects housing 28 to pump housing I8, rotation of housing 28 being prevented by a link 30 which connects it to crossbeam Hi.

The enclosure for drive i l and the arrangement for supporting pump I0 do not per se form any part of the present invention but are fully disclosed and claimed in my co-pending application Serial No. 576,242 filed February 5, 1945 to which reference may be had for details of construction.

Motor 3 and pump I0 are preferably of the sliding vane type for the reason that a hydrodynamic machine of that type has. a greater volumetric capacity per unit of weight than a piston type machine. In a pump of the sliding vane type, a major volume of liquid is displaced by the outer end portions of the vanes and a minor volume of liquid is displaced by. the inner ends of the vanes. In the present instance, the major volume is employed to drive motor 3 and the minor volume is employed principally to hold the motor vanes against the vane track of motor 3 so that two separate circuits are required.

Each side of each circuit must include a flexible portion for the reason that pump I0 moves relatively to motor 3 when the car is in motion. Each flexible portion may comprise a length of flexible hose but for the purpose of illustration the circults have been shown as including two slide pipes 35 and 36 having one end of each connected to pump housing l8 and the other end of each connected to a manifold 31 which is fixed to car body 2 and connected to motor 3 by four fluid channels 38, 39, 49 and 4|.

The liquid in slide pipes 35 and 36 exerts forces which tend to move pump housing I8 and manifold 31 away from each other and those forces are counterbalanced at least in part by a hold-up mechanism comprising a cylinder 42, which is fixed to pump housing l8, and a rod 43 which is connected by universal joints to manifold 31 and to a piston (not shown) which is fitted in cylinder 42 and continuously subjected to pump pressure.

Slide pipes 35 and 36 and hold-up mechanism 42-43 have not been shown in detail as they are fully illustrated and described in the above mentioned application to which reference may be had for the specific construction thereof. Slide pipes 35 and 36 are specifically claimed in Patent No. 2,462,734.

It is deemed suflicient to state herein that slide pipes 35 and 36 are extensible and contractible in length, that each is bendable at two points and that each contains a high pressure channel and a low pressure channel.

As shown schematically in Fig. 5, slide pipe 35 contains a large capacity high pressure channel 44, which communicates through manifold 31 with channel 38 on car body 2, and a smaller capacity low pressure channel 45 which communicates through manifold 31 with channel 39 on car body 2. Slide pipe 36 contains a small capacity high pressure channel 46, which communicates through manifold 31 with channel 46 on car body 2, and a larger capacity low pressure channel 41 which communicates through manifold 31 with channel 4| on car body 2.

The arrangement is such that the liquid for driving motor 3 flows through channels 44 and 38, the liquid discharged by motor 43 flows through channels 4| and 41, the liquid discharged by the inner ends of the pump vanes" flows through channels 46 and 48, and the liquid discharged by the inner ends of the motor vanes flows through channels 39 and 45.

Pump ID has its rotor 56 (Fig. 4) fixed upon a shaft 5| to which drivel I (Fig. l) is connected so that rotor 50 is rotated at varying speeds in one direction or the other in response to movement of the car at varying speeds in one direction or the other.

Pump ID has been shown as being of the type illustrated and described in application Serial No. 537,346 filed May 25, 1944 to which reference may be had for specific details of construction. It is deemed suilicient to state herein that rotor 56 is arranged within a spacer ring 52 and provided with a plurality of radial vane slots 53 each of which has a vane 54 slidably fitted therein. Dur ing rotation of rotor 50, the outer ends of vanes 54 ride upon a vane track which is approximately elliptical when the pump is functioning. The vane track is formed by two diametrically opposed bridges 55, two bridges 56 which are spaced 90 from bridges 55, and four extensible vane track sections 51 each of which is arranged between adjacent bridges and pivotallyconnected thereto.

The space between the vane track and the periphery of rotor 50 communicates through track sections 51 with two diametrically opposed low pressure or intake ports 58 and with two diametrically opposed high pressure or discharge ports 59 each of which is formed in spacer ring 52 between adjacent bridges.

Spacer ring 52 is tightly clamped between two cheek plates (not shown) one of which has openings extending therethrough from ports 58 and 59 into communication with fluid channels which are formed in pump housing I8 and lead to the inlet and outlet ports of pump I0. As shown schematically in Fig. 5, both low pressure ports 58 communicate with a channel 60 to which channel 4'! in slide pipe 36 is connected, and both high pressure ports 59 communicate with a channel 6| to which channel 44 in slide pipe 35 is connected.

The inner ends of vane slots 53 in rotor 50 '(Fig. 4) register selectively with vane slot ports which are formed in the inner face of a cheek plate and communicate through the cheek plate with fluid channels formed in pump housing l8 and constituting parts of the vane root circuit. As shown schematically in Fig. 5, channel 45 in slide pipe 35 communicates with a. channel 62 which leads to two diametrically opposed vane slot ports 63 which are formed in the inner face of a cheek plate inward from ports 58, and channel 46 in slide pipe 36 communicates with a channel 64 which leads to two diametrically opposed vane slot ports 65 which are formed in the inner face of the cheek plate inward from ports 59.

The outer portions of bridges 55 and 56 are arranged, respectively, in recesses 68 and 69 (Fig. 4) which are formed in spacer ring 52. The outer portion of each bridge is closely fitted in a recess and closely fitted between the cheek plates so that the outer portion of the bridge functions as the piston and the recess functions as the cylinder of a servomotor for moving the bridge inward and for controlling the outward movement thereof, each bridge being constantly urged outward by springs (not shown) and also being urged outward by forces exerted upon the vane track by the liquid when the pump is creating pressure.

Bridges 55 and 56 are adapted to be moved inward or permitted to move outward by liquid delivered to or permitted to escape from their recesses under the control of two follow-up type pilot valves 10 and two follow-up type pilot valves H which are fitted, respectively, in bridges 55 and 56 and of which only the stems have been shown. I

The arrangement is such that, when the pilot valve of a bridge is moved inward, liquid will enter the recess in which that bridge is fitted and will move that bridge inward the same distance that the pilot valve was moved inward and then that bridge will cut off further flow of liquid to the recess and movement of the bridge will cease. When the pilot valve of a bridge is moved out-. ward, liquid will escape from the recess in which that bridge is fitted and will permit that bridge to move outward the same distance that its pilot valve was moved outward and then that bridge will cut ofi' further escape of liquid from the recess and movement of the bridge will cease.

Pilot valves 10 and H are operated by a cam ring 12 which extends around spacer ring 52 and has two diametrically opposed cam grooves I3 and two diametrically opposed cam grooves 14 formed in its inner peripheral surface. Cam grooves 13 are located at such angular distances from cam grooves 14 that, when cam ring 12 is in its neutral position, each pilot valve stem engages a concentric portion of cam ring 12 at the end of a cam groove so that a sli ht rotation of cam ring 12 from its neutral position in one direction permits the stems of pilot valves 18 to move outward along cam grooves 13 and a slight rotation of cam ring 12 from its neutral position in the opposite direction permits the stems of pilot valves H to move outward along cam grooves 14. Cam ring 12 is adapt-ed to be rotated by mechanism to be presently described.

Liquid for, operating bridges 55 and 56 when pump pressure is low or absent and for keeping both the main circuit and the vane root circuit flooded is supplied by a gear pump 15 which is driven in unison with the main pump and arranged in the casing thereof. In the present instance, rotor 58 of the main pump is driven in one direction or the other in response to movement of the car in one direction or the other so that ear pump 15 is also driven in opposite directions alternately but it must deliver liquid in only one direction.

As shown schematically in Fig. 5, gear pump '15 has its opposite sides connected to two channels l6 and H adjacent ends of which ar connected, respectively, through two check valves 18 and 19 to a channel extending into a reser voir 8| which may be arranged within crossbeam l4. Check valves 18 and 19 permit pump I5 to draw liquid from reservoir 8| into either channel 16 or channel H but prevent pump I5 from discharging liquid into reservoir 8|.

The other ends of channels 16 and 11 are connected. respectively, through two check valves 82 and 83 to a branched channel 84 which has one branch thereof connected to channel 62 and another branch thereof connected to pilot valves I and H through channels not shown. Check valves 82 and 83 permit gear pump 15 to discharge liquid through either channel I6 or channel 11 into channel 84 but prevent flow of liquid from one to the other of channels 16 and 11.

The arrangement is such that, when gear pump 15 is driven in One direction, it will draw liquid from reservoir 8| through channel 80, check valve 18 and channel 16 and discharge it through channel 11 and check valve 83 into channel 84 and, when gear pump 15 is driven in the opposite direction, it will draw liquid from reservoir 8| through channel 80, check valve 19 and channel I1 and discharge it through channel I6 and check valve 82 into channel 84.

A part of the liquid discharged by gear pump 15 into channel 84 flows to channel 62 to keep the vane root circuit flooded. another part flows when needed to pilot valves and H to effect operation of bridges 55 and 56, and the remainder of the liquid discharged by gear pump flows through a resistance valve 85 into a channel 86 which is connected to channel 60. A part of the 7 of the vane root circuit and in channel 84 a pressure equal to the sum of the resistances of valves 85 and 81. The pressure in channel 84 is suflicient to operate bridges 55 and 56 until it is exceeded by the pressure created by m I0 and then bridges 55 and 56 are operated by liquid supplied by pump lll as explained in application Serial No. 537,346.

When bridges 55 and 56 are in the positions shown in Fig. 4 and rotor is rotated in a clockwise direction, the vanes will move outward as they travel from inward bridges 56 to outward bridges 55. The spaces between the outer portions of the outward moving vanes will be filled with liquid from intake ports 58 and this liquid will be expelled into discharge ports 59 as the vanes travel from outward bridges to inward bridges 56 and are forced inward by the vane track. Pump It will thus discharge liquid at the maximum rate at that particular speed of rotor 50 for the reason that bridges 56 are in their innermost positions with the track surfaces thereon close to the periphery of rotor 50 and bridges 55 are in their outermost positions with, the track surfaces thereon spaced the maximum distance from the periphery of rotor 50 so that pump displacement is maximum. The outward moving vanes are held in contact with the vane track by the pressure maintained in vane slot ports 63 by gear pump 15 and the inward moving vanes will expel liquid from their slots into vane slot ports If cam ring 12 is rotated in a clockwise direction from the position shown in Fig. 4, pilot valves 10 will be pushed inward by cam grooves 13 and cause bridges 55 to move inward, thereby decreasing pum displacement and consequently decreasing the rate of pump delivery at any given speed. During continued rotation of cam ring I2, bridges 55 will continue to move inward until cam ring I2 reaches its neutral position and then all four bridges will be in their innermost positions so that pump displacement is zero. Rotation of cam ring 12 beyond its neutral position will permit the stems of pilot valves 'II to move outward along cam grooves and cause bridges 56 to move outward, thereby reversing the pump.

If rotor 50 continued to rotate in the same direction after bridges 56 were moved outward, pump would discharge in the opposite direction but in the present instance the pump is eversed Only in response to reversal of the direction of rotation of rotor 50 so that pump I0 always delivers liquid in the same direction. That is, bridges 55 are moved outward only when rotor 58 is driven in a clockwise direction and bridges 56 are moved outward only when rotor 50 is driven in a counterclockwise direction so that pump I0 always discharges liquid through its discharge ports 59.

Cam rin 12 is adapted to be rotated in one direction or the other by a control which is arranged within control housing Il (Fig. l) and is shown schematically in Fig. 4.. The control includes two flow responsive devices SI and 9| one or the other of which is first operated and effects rotation of cam ring I2 to one or the other of its maximum displacement positions in response to pump It being driven in one direction or the other and the previously unoperated device will thereafter rotate cam ring 12 in a direction to reduce pump displacement in response to pump l0 being driven at speeds above an intermediate speed.

Device 9I includes a plunger 92 which is fitted in a stationary cylinder 93 and has a piston 94 fixed to or formed thereon and fitted in a counterbore 95 formed in the body of cylinder 93 concentric with the bore thereof. Plunger 92 is urged inward and normally held against the head end of cylinder 93 by a spring 96 arranged between its outer end and a stationary abutment 97. Plunger 92 is adapted to be moved outward by liquid delivered to the head end of cylinder 93 as will presently be explained, outward movement of plunger 92 being limited by a stop 98 which is fixed to cylinder 93 and adapted to be engaged by piston 94.

Cylinder 93 has an annular groove or port 99 formed in the wall of its bore at its inner end, an annular groove or port I60 formed in the wall of its bore and spaced from port 99, and an annular groove or port |0I formed in the wall of counterbore 95 at the inner end thereof. Communication between ports 99 and N10 is provided by a plurality of tapered grooves I02 which are formed in the peripheral surface of plunger 92 at the inner end thereof and permit restricted flow from port 99 to port I 00. Communication between port 99 and port Illl is provided by a passage I03 which extends axially into plunger 92 from the inner end thereof and then extends radially outward at such a point that it registers with port I0| when plunger 92 is in its outermost position.

Device 9| is substantially the same as device 9| and a description thereof is deemed unnecessary since like parts have been indicated by like reference numerals with the exponent (1" added to the reference numerals applied to device 9 I.

In order that cam ring 12 may be adjusted by one and the adjustment modified by the other of devices 9| and 9|, a floating lever I04 has its ends rounded and fitted in two slots I94 and I05 formed in the outer portions of plungers 92 and 92 respectively. Lever I04 is pivotally connected at its center to one end of a link I96 which has its other end pivoted to cam ring 12. The arrangement is such that, when one of the two plungers such as plunger 92 is moved outwardto the limit of its movement, lever I04 will pivot in the slot in the other plunger and cause link I06 to rotate cam ring 12 in one direction to a maximum displacement position and then, when the other plunger such as plunger 92 is moved outward a limited distance, lever I04'wi1l pivot in the slot of the first plunger and cause link I06 to rotate cam ring 12 a limited distance in the .opposite direction and thereby reduce pump dis- Gear pump I I has its opposite sides connected t two channels III and H2 the lower ends of which are connected, respectively, through two check valves H3 and H4 to a channel H5 which extends into reservoir BI. Check valves H3 and H4 permit gear pump H0 to draw liquid from reservoir BI into either channel III or channel H2 but prevent gear pump IIO from discharging into reservoir 8|.

Flow of liquid from gear pump IIO to devices 9| and 9| is controlled by a valve H6 which is fitted in the bore of valve casing H'I having five annular grooves or ports I I8, I I9, II 9, I20 and I20 formed in the wall of its bore and channels III and H2 connected, respectively, to opposite ends of its bore. Valve casing H1 is symmetrical about its transverse centerline and port H8 is located upon the centerline and communicates with a channel I2I which discharges into reservoir 8|.

- 99, grooves I02,

Ports H9 and H9 are arranged at opposite sides of port H8 and are connected, respectively, by channels I22 and I22 to ports I00 and I00 in devices 9i and 9| respectively. Ports I20 and I20 are spaced from ports H9 and H9, respectively, and are connected to ports 99 and 99 in devices 9I and 9| by channels I 23 and I 23 respectively. Port IOI in device 9I is connected to channel I23 at a point intermediate the ends .thereof by channel I24 having a check valve I25 arranged therein. Port IOI in device 9| is connected to channel I23 at a point intermediate the ends thereof by a channel I24 having a check valve I25 arranged therein.

When gear pump I I0 is rotated in one direction, it will draw liquid from reservoir 8I through channel I I5, check valve I I4 and channel H2 and discharge it into channel I I I. Since check valve I I3 prevents the liquid from being discharged into reservoir 8 I, the liquid will flow to the end of valve casing II'I, move valve I I6 downward in respect to the drawing and then flow through channel I23 to port 99.and advance plunger 92 for the reason that check valve I25 prevents the liquid from flowing through channel I24. Advancing plunger 92 opens passage I 03 to port I 0| and then the liquid will flow therethrough and through channels I24 and I23, port 99, grooves I02, port I00, channel I22, valve casing II! and channel I2I to reservoir 9| and effect operation of device 9i in response to the car reaching a predetermined speed as will presently be explained.

When gear pump H0 is rotated in the opposite direction, it will draw liquid from reservoir 9| through channel I I5, check valve I I3 and channel III and discharge it into channel H2. Since check valve -II4 prevents the liquid from being discharged into reservoir BI, the liquid will flow to the end of valve casing I", move valve I I6 upward in respect to the drawing and then flow through channel I23 to port 99 and advance plunger '92 for the reason that check valve I25 prevents liquid from flowing through channel I24. Advancing plunger 92 opens passage I03 to port I01 and then the liquid will flow therethrough and through channels I24. and I23. port port I00, channel I22, valve casing I I1 and channel I2I to reservoir I8 and effect operation of device 9I in response to the car reaching a predetermined speed as will presently be explained.

Motor 3 may be a constant displacement motor and its speed may be maintained substantially constant by varying the displacement of pump I0 inversely to the variations in car speed above an intermediate speed. However, a constant displacement motor just large enough to drive the car lighting and air conditioning apparatus when supplied with liquid at a maximum pressure would have to operate at that maximum pressure during the entire time it was driving the car lighting and air conditioning apparatus. Also, a constant displacement motor large enough to drive the car lighting and air conditioning apparatus when supplied with liquid at a lower pressure would require a larger pump in order to maintain motor speeds substantially constant at all car speeds above an intermediate speed-by varying the displacement of pump inversely to variations in car speed above that intermediate speed.

It is therefore desirable to employ a variable displacement motor which will drive the car lighting and air conditioning apparatus when motor displacement is considerably less than maximum and which will automatically'increase its displacement when the car is running at high speeds so that'the pump and the motor will operate at high pressures for onlyv short intervals and will operate at lower pressures during the greater part of the time that the motor is driving the car lighting and air conditioning apparatus.

For the purpose of illustration, motor 3 has been shown as having an internal construction substantially the same as that of pump I0 except that its bridges are not operated hydraulically under the control of pilot valves as in pump I 0. Therefore, corresponding parts have been indicated by corresponding reference numerals with the exponent a added to the reference numerals applied to motor 3 and only a brief description is deemed necessary.

As shown in Fig. 3, motor 3 has its rotor 50! fixed upon a shaft I3I which, as indicated in Fig. 1, is connected through clutch 4 to the car lighting and air conditioning apparatus. Rotor 50 is arranged within a spacer ring 52 and provided with a plurality of radial vane slots 53 each of which has a vane 54 slidably fitted therein. The engage a substantially" outer ends of vanes 54 elliptical vane track formed by two diametrically opposed movable bridges 55, two stationary bridges 56 which are spaced from bridges .55, and four extensible vane track sections 51 each of which is arranged between adjacent bridges and pivotally connected thereto.

Two diametrically opposed inlet ports 58 and two diametrically opposed outlet ports 59 are formed in spacer ring 52 which is clamped between two cheek plates not shown. As shown schematically in Fig. 5, both inlet ports 55 communicate through openings in'one of the cheek plates with a, fluid channel 60 which is formed in the motor housing and has channel 38 connected thereto, and both outlet ports 59- communicate through openings in one of the cheek plates with a fluid channel 6| which is formed in the motor housing and has channel 4I connected thereto.

The inner ends of vane slots 53 register selectively with two diametrically opposed vane slot ports 63 and two diametrically opposed vane slot ports 55 which are formed in the inner face of a cheek plate inward from ports 58* and 59 respectively. Ports 63 are both connected to channel 40 by a channel 62 formed in the motor housing, and ports I35 are both connected to channel 39 by a channel I54 formed in the motor housing.

Bridges 55 (Fig. 3) have the outer portions thereof slidably fitted in recesses 68 which are formed in spacer ring 52 but bridges 56 are rigidly secured in spacer ring 52- instead of being slidable therein as are bridges 56 of pump Ill. The outer portions of bridges 55 are closely fitted between the two cheek plates and in recesses I58 and form therewith substantially fluid tight slidable joints to prevent leakage of liquid from the interior of the motor. Instead of bridges 55 being moved inward and outward in response to liquid flowing to and from their recesses under the control of pilot valves as in pump I0, they are adapted to be moved outward by the pressure of the motive liquid acting upon the inner faces thereof and they are adapted to be moved inward mechanically by mechanism to be presently described, the outer ends of recesses 68 being drained to prevent entrapment of air and leakage liquid.

Motor 3 thus has an internal construction similar to that of pump I except for the means for operating the bridges but it functions oppositely to pump I0. That is, liquid discharged by pump I0 flows through channels SI, 44, 38 and 60 and ports 58, across the faces of bridges 55 and through ports 59- and channels 6|, 4t, 41 and 60 to intake ports 58 of pump Ill. The vanes in contact with bridges 55 are carried thereacross by the liquid and cause rotor 50 to rotate and moves succeeding vanes into contact with bridges 55 so that rotor 50 is rotated continuously and drives shaft I3I 'at a speed determined both by the rate at which liquid is delivered to motor 3 and by the displacement of motor 3.

Vanes 54 must move outward as the outer ends thereof travel from a bridge 56 to a bridge 55 and they'are forced inward as the outer ends thereof travel from a bridge 55 to a bridge 56. The liquid expelled by the inward moving pump vanes 54 from their slots into vane slot ports 65 flows therefrom through channels 64, 45, and 62 and vane slot ports 63 into the slots of the outward moving motor vanes 54 and holds those vanes in contact with the vane track, and the inward moving motor vanes 54 eject liquid from their slots through ports 65, passages 64, 39, and 62 and vane slot ports 63 into the slots of the outward moving pump vanes 54.

Since the outer ends of the outward moving motor vanes 54 are subjected to pump pressure, the inner ends thereof must be subjected to a higher pressure in order to move the vanes outward and positively hold the outer ends thereof in contact with the vane track. This is accomplished by providing a pump having a total vane displacement greater than the total vane displacement of the motor such as by making pump vanes 54 slightly thicker than motor vanes 54. The volume of liquid pumped by the inner ends of the pump vanes is thus in excess of the volume required to move the motor vanes outward and the excess is exhausted from the high pressure side of the vane root circuit into the high pressure side of the main circuit such as by connecting a resistance valve I32 between channels 64 and BI so that the inner ends of the outward moving motor vanes are subjected to a pressure which exceeds the pressure to which the outer ends thereof are subjected by an amount equal to the resistance of valve I32. The pressure in the main-circuit is limited to a predetermined maximum such as by connecting a relief valve I33 between channels and GI.

Motor 3 is provided with a control which will maintain the motor speed substantially constant after it reaches a predetermined maximum, such as the control shown schematically in Fig. 3. That control includes two push rods I40 and I each of which engages the outer end of a bridge 55 and is slidably fitted in spacer ring 52 and in a wall of the motor housing.

The outer end of push rod I40 engages the lower end of a lever I42 which is pivoted intermediate its ends upon a shaft I43 carried by the motor housing, and the outer end of push rod I4I engages an intermediate portion of a lever I44 which is pivoted at its lower end upon a shaft I45 carried by the motor housing so that moving the upper ends of both levers toward the right causes both of bridges 55 to be moved inward and moving the upper ends of both levers toward the left permits both of bridges 55* to be moved outward by pressure acting upon the inner faces thereof.

The upper ends of levers I42 and I44 are connected, respectively, by two links I46 and I41 to two piston rods I48 and I49 fixed to opposite ends of a piston I50 which is fitted in a stationary cylinder I5! and urged toward the right by a spring I52 having suflicient strength to effect inward movement of bridges 55 when the pressure within motor 3 is very low. Piston I50 is also adapted to be moved toward the right by liquid supplied to cylinder I5I through a channel I53 from the high pressure side of the main circuit. Piston I50 and levers I42 and I44 are so proportioned that, when cylinder I5I is supplied with liquid, piston I50 and spring I52 will move bridges 55 inward against the forces exerted upon the inner faces thereof by the liquid within motor 3. I

Inward movement of bridges 55 is limited by a stop screw I54 which engages lever I42 and is adjusted to stop further inward movement of bridges 55 when motor displacement has been reduced to a predetermined minimum, such as one half of maximum displacement. Outward movement of bridges 55 is limited by a stop screw I55 which engages lever I44 and is adjusted to stop further outward movement of bridges 55 when motor displacement has been increased to a predetermined maximum, such as full displacement.

Liquid flows through channel I53 to and from cylinder I5I under the control of a pilot valve I60 having three spaced apart heads or pistons IBI, I62 and I83 fixed or formed thereon and closely fitted in the bore of the valve casing I54. Piston IBI controls communication between channel I53, which is connected to valve casing I54 at or near the center thereof, and a channel I55 which has one end connected to valve casing I64 at a point between pistons I6I and I62 and its other end connected to the high pressure side of the main circuit such as by being connected to passage 60 as shown in Fig. 5. Piston I6I also controls communication between channel I53 and a drain channel I66 which is connected to valve casing I64 at a point between pistons I6I and I63 and discharges into the housing of motor 3. Liquid discharged or leaking into the housing of motor 3 is drained into reservoir 8I through channels not shown.

Pilot valve I60 is controlled by a speed responsive device which may be of the type shown schematically in Fig. 3 and which may be enclosed with the pilot valve within a housing I61 arranged upon the housing of motor 3 as shown in Fig. l. The speed responsive device chosen for illustration includes a floating lever I68 which has one end pivoted to the stem of pilot valve I60 and its other end connected by a pin and slot connection to the case I69 of a differential I69. Lever I68 is pivotally connected intermediate its ends to one end of a follow-up rod I10 which is slidable in suitable guides and has its lower end urged by a spring I1'I against a cam I12 fixed to or formed upon piston rod I49.

Differential I69 has not been illustrated in detail as it is a well known three legged type. It is deemed sufiicient to state herein that differential case I69 is mounted for rotation upon I adjacent end portions of two shafts I69 and I69 which are journaled in suitable bearings and constitute the first and second legs of the differential. Case I69, which constitutes the thirdleg of the differential, encloses a gear mechanism for transmitting motion from either shaft to the case. For .the purpose of this explanation, it will be assumed that the gear mechanism is such that case I69 will remain stationary when shafts I69 and I69 are driven at the same speed but will rotate in response to one shaft rotating through a greater angular distance than the other shaft.

Shaft I69 is driven from motor shaft I3I through a suitable drive I13. and shaft I 69 is driven through reduction gears I14 and I15 and a slipping clutch I16 by a small constant speed electric motor I11. Drive I13 and gears I14 and I15 are so proportioned that, when motor 3 is operated at the correct speed for driving the car lighting and air conditioning apparatus, shafts I69 and I69 will be driven at the same speed and differential case I69 will remain stationary and-hold pilot valve I60 in such a position that piston I6I blocks the end of channel I53 so that liquid cannot flow to or from cylinder'I5I to effect a change in the displacement of motor 3.

Motor 3 does not operate fast enough to drive the car lighting and air conditioning apparatus at the proper speed until the car reaches an intermediate speed but electric motor I11-operates continuously at a substantially constant speed and tends to keep differential case I69 rotating whenever the speed of motor 3 is too low. In order to prevent differential case I69 from being rotated a material angular distance beyond its operating range, rotation thereof is prevented by suitable stops and slipping clutch I16 is provided.

As shown, an abutment I18 fixed to differential case I69 is adapted to engage a stop screw I19 just as or just after case I69 reaches one end of its operating range, and if desired, a second abutment I80 may be provided to engage a second stop screw (not shown) just as or just after the diflerential case reaches the other end of its operating range.

The arrangement is such that, when the car is stationary so that motor 3 is idle and is preventing rotation of shaft I69, energizing electric motor I11 will cause it to drive differential I 69 until abutment I18 engages stop screw I19 and then clutch I16 will slip and permit motor I11 to operate without driving diiferential I69.

Operation When the car is stopped temporarily at a station, pump I0 and motor 3 will be idle and the car lighting and air conditioning apparatus will be driven by the D. C. motor-generator. When the car starts to move in one directi'on or the other, pump I0 will be driven in one direction or the other but it will deliver liquid in only one direction regardless of the direction in which it is driven and the liquid discharged by pump I0 will flow through channels GI, 44, 38 and 60 and cause motor 3 to operate in a clockwise direction as previously explained, the liquid discharged by motor 3 being returned through channels 6|, 4|, 41 and 60 to pump I0.

Motor 3 will drive shaft I3I but the D. C. motor-generator will continue to drive the car lighting and air conditioning apparatus for the reason that pump I0 even at maximum displacement cannot deliver enough liquid to cause motor 3 to operate fast enough to drive the car lighting and air conditioning apparatus at the correct speed until the car has accelerated to a predetermined intermediate speed, such as 25 M. P. H.

It has previously been explained that the flow control mechanism shown in Fig. 4 causes pump I0 to discharge liquid in one direction only regardless of the direction of car movement. Since the two halves of the flow control mechanism are identical and function in exactly the same manner, it is believed that an explanation of the operation of the drive during moyement of the car in one direction will suffice.

Assuming that the car moves in a direction to cause pump I0 to be driven in a clockwise direction in respect to Fig. 4, gear pump IIO will be driven in the same direction and the liquid discharged thereby will flow through channel III, valve casing H1 and channel I23 to cylinder 93 and move plunger 92 downward against the resistance of spring 96 until p s e I03 Opens to port IOI so that the liquid can then flow through channel I24 into channel I23. Since port I 20*- is at this time blocked by valve I I6, the liquid entering channel I23 will flow therethrough and through grooves I02 channel I22 valve casing H1 .and channel I2I to reservoir 8|. Plunger 92 in moving downward will carry the left end of lever I04 with it and causelink I06 to rotate cam ring 12 counterclockwise until the displacement of pump I0 is substantially maximum as previously explained.

Since pumps I0 and H0 are driven from an axle of the car, the speeds thereof will be proportional to the speed of the car. Therefore, the rate at which pump I0 delivers liquid will increase with and be proportional to the car speed as long as its displacement remains constant, and the rate at which pump III) delivers liquid will increase with and be proportional at all times to the car speed for the reason that pump IIO has a constant displacement.

When plunger 92 is in its innermost position, the effective area of grooves I02 are large enough to pass the entire volume of liquid discharged by 15 pump IIO without causing the pressure therein to become high enough to raise plunger 92'- against the resistance of spring 96 until the car reaches a predetermined intermediate speed, such as 25 M. P. H.

As the car speed increases above the intermediate speed, the output of pump IIO correspondingly increases and causes pressure to rise sufficiently to move plunger 92 upward and thereby increase the effective areas of grooves I02 sufficiently to accommodate the increased flow of liquid. Plunger 92"- in moving upward will carry the right end of lever I04 with it and thereby cause link I06 to rotate cam I2 clockwise to reduce the displacement of pump I0.

If a constant displacement motor is employed to drive the car lighting and air conditioning apparatus, grooves I02 are of such size and have such a taper that the liquid flowing therethrough at car speeds above the intermediate speed causes plunger 92 to rise and reduce the displacement of pump II] in proportion to the increase in car speed so as to maintain the output of pump I substantially constant and thereby maintain the motor speed substantially constant.

If a variable displacement motor is employed as shown, grooves I02 are of such size and have such a taper that liquid flowing therethrough at car speeds above the intermediate speed causes plunger 92 to rise and reduce the displacement of pump I0 at a rate less than the rate of car acceleration and the speed of the motor is maintained substantially constant by varying motor displacement in response to the motor speed tending to vary from the correct speed.

In the drive chosen for illustration, the parts have been shown in the positions occupied when the car is running at a speed less than the predetermined intermediate speed. As shown, flow control device BI has adjusted pump I0 to maximum displacement, pump I0 is delivering liquid to motor 3 which is operating at a speed less than the correct speed for driving the car lighting and air conditioning apparatus, spring I52 is maintaining the displacement of motor 3 at the predetermined minimum, motor 3 is driving shaft I69 at slow speed, electric motor I1! is driving shaft I69 and tending to drive it faster than shaft I69 so that abutment I78 is held against stop screw I19, and clutch H6 is slipping to permit motor I'I'I to operate at full speed.

As the car speed increases, the output of pump I0 and consequently the speed of motor 3%Will increase proportionally until at the intermediate speed motor 3 will run fast enough to pick up the load through overrunning clutch 4. Picking up the load will cause pump pressure to rise enough to enable motor 3 to drive the car lighting-and air conditioning apparatus and this pressure will extend through channel I65, pilot valve casing I64 and channel I53 to cylinder II and enable piston I 50 to prevent bridges 55 from being moved outward by the pressure acting upon the inner faces thereof.

After the car reaches the intermediate speed, pump in will continue to deliver liquid to motor 3 at a rate in excess of the rate required to drive it at the correct speed. Motor 3 will therefore tend to accelerate and it will rotate shaft I69 through a greater angular distance than shaft l69 is being rotated by constant speed motor I", thereby causing difierential case I69 to rotate a limited angular distance counterclockwise and to move the right end of lever I68 down- Ward.

Lever I68 will pivot upon follow-up rod I10 and raise pilot valve I60 until piston I6I thereon first blocks the end of channel I53 and then opens a small lower portion thereof to drain channel I66 to permit liquid to escape from cylinder I5I so that the pressure within motor 3 may move bridges 55 outward to increase the motor displacement and thereby prevent the motor speed from increasing beyond the correct speed as determined by constant speed motor I".

Bridges :55 in moving outward will swing levers I42 and I44 upon shafts I43 and I45 respectively, the upper ends of the levers will move piston I50 toward the left, piston I50 will eject liquid from cylinder I5I through channel I53 and valve casing I64 into drain channel I66; and the movement of piston I50 will be regulated by piston I6I throttling the flow from channel I53. Cam In will move with piston I and permit followup rod I10 to move downward and lower the pivot point of lever I68 so that follow-up rod I10 tends to move pilot valve I downward as fast as differential I69 tends to move it upward. Consequently, when the car speed becomes uniform so that pump I0 is delivering liquid to motor 3 at a constant rate, piston I6I will block the end of channel I53 and prevent further adjustment of motor 3.

When the car speed decreases, the rate at which pump I0 delivers liquid to motor 3 will correspondingly decrease and cause motor 3 to tend to declerate but, as soon as motor 3 tends to decelerate, it will rotate shaft I60 through a lesser angular distance than shaft I69 is being rotated by motor I", thereby causing differential case I69 to rotate a limited angular distance clockwise and to move the right end of lever I68 upward.

Lever I68 will pivot upon follow-up rod I10 and move pilot valve I60 downward to slightly open the end of channel I53 to channel I and then liquid from the high pressure side of the circuit will flow through channel I65, valve casing I64 and channel I53 to cylinder I5I and cause piston I50 to move toward the right and effect a reduction in motor displacement corresponding to the reduction in the rate of liquid flow so as to maintain the motor speed substantially constant. Cam I12 will move with piston I50 and raise follow-up rod I10 and thepivot point of lever I68 so that follow-up rod I10 tends to move pilot valve I60 upward as fast as differential I69 tends to move it downward. Consequently, if the car speed again becomes uniform so that pump I0 is delivering liquid to motor 3 at a constant rate, piston I6I will block the end of channel I53 and prevent further adjustment of motor 3. If the car speed continues to decrease, differential I69 will continue to effect reduction of motor displacement and thereby.

maintain motor speed substantially constant until the car speed drops below the predetermined intermediate speed and then the car. lighthydraulic motor and varying the displacements of both the pump and the motor to maintain the motor speed substantially constant, a constant displacement motor may be employed and its speed maintained nearly constant by varying pump displacement inversely to variations in pump speed as previously explained.

If it is desired to maintain the speedof a constant displacement motor more nearly constant than is practical by varying the displacement of the pump, pump displacement may be varied inversely to variations in pump speed to cause the pump to deliver liquid to the motor at a substantially constant rate, and a small percentage of the motive liquid may be bypassed around the motor under the control of a bypass valve which is shifted to vary the flow of bypassed liquid in response to the motor speed tending to vary from a predetermined constant.

This could readily be accomplished by using the speed responsive mechanism shown in Fig. 3 as itwould only be necessary to substitute a bypass valve for pilot valve l 60 and to cause follow- 18 relative to said constant speed causes movement of the third leg of said differential, and means for operating said pilot valve in response to movement of said third leg.

4. In a hydraulic drive, the combination of a variabledisplacement pump adapted to be driven at varying speeds, avariable displacement hydraulicv motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said pump in response to variations in the speed thereof, means for varying the displacement of said motor between a minimum and a maximum, hydraulic means for operating said motor displacement varying means, a pilot valve for controlling said hydraulic means, a differential having one leg driven by said motor and a second leg driven at a substantially constant speed so that a variation in motor speed relative to said constant speed causes movement of the third leg of said differential, means responsive to movement of said third leg for shifting said pilot valve in one direction or the other up rod I10 to move in response to movement of the valve. ous from the foregoing description, it has not been illustrated.

The invention herein set forth is susceptible of various modifications and adaptations without departing from the scope thereof. The indraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said pump in response to variations in the speed thereof, and means responsive to the speed of said motor varying from a predetermined speed for varying the displacement of said motor to thereby maintain said predetermined motor speed substantially .constant during operation of said pump at speeds above a predetermined minimum speed.

2. In a hydraulic drive, the combination of a variable displacement pump adapted to be driven at varying speeds, a variable displacement hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said pump in response to variations in the speed thereof, means for varying the displacement of said motor between a minimum and a maximum, hydraulic means for operating said motor displacement varying means, a pilot valve for controlling said hydraulic means, and means responsive to the speed of said motor varying from a predetermined speed for operating said pilot valve.

3. In a hydraulic drive, the combination of a variable displacement pump adapted to be driven at varying speeds, a variable displacement hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said pump in response to variations in the speed thereof, means for varying the displacement of said motor between a minimum and a maximum, hydraulic means for operating said motor displacement varying means, a pilot valve for controllin said hydraulic means, a differential having one leg driven by said motor and a second leg driven at a substantially constant speed so that a variation in motor speed Since such a construction is obvifrom a neutral position to cause said hydraulic means to operate said motor displacement varying means, and means responsive to operation of said hydraulic means for returning said pilot valve to its neutral position.

5. In a hydraulic drive, the combination of a reversible variable displacement pump adapted to be driven in one direction or the other, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, and means for reversing said pump in response to a change in the direction in which said pump is driven to thereby cause said pump to deliver liquid to one side only of said motor and said motor to operate in only one direction regardless of the direction in which said pump is driven.

6. In a hydraulic drive, the combination of a reversible variable displacement pump adapted to be driven in one direction or the other, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for reversing said pump in response to a change in the direction in which said pump is driven to thereby cause said pump to deliver liquid to one side only of said motor and said motor to operate in only one direction regardless of the direction in which said pump is driven, and means for thereafter varying 'the displacement of said pump inversely to variations in pump speed to thereby avoid corresponding variations in the speed of said motor.

7. In a hydraulic drive, the combination of a reversible variable displacement pump adapted to be driven in one direction or the other, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means tending to adjust said pump to zero displacement, and means responsive to said pump being driven in one direction or the other for adjusting said pump to cause it to discharge in the same direction and said motor to operate in only one direction regardless of the direction in which said pump is driven.

8. In a hydraulic drive, the combination of a reversible variable displacement pump adapted to be driven in one direction or the other, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means tending to adjust said pump to zero displacement, means responsive to said pump being driven in one direction or the other for adjusting said pump to cause it to discharge in the same direction and said motor to operate in only one direction regardless of the direction in which said pump is driven, and means for thereafter varying the displacement of said pump inversely to variations in pump speed to thereby avoid corresponding variations in the speed of said motor.

9. In a hydraulic drive, the combination of a reversible variable displacement pump adapted to be driven in one direction or the other, a'hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for reversing said pump in response to a change in the direction in which said pump is driven to thereby cause said pump to deliver liquid to one side only of said motor and said motor to operate in only one direction regardless of the direction in which said pump is driven, and means operable only after the speed of said pump has reached a given value for varying pump displacement inversely to variations in pump speed above that value to thereby avoid corresponding variations in the speed of said motor.

10. In a hydraulic drive, the combination of a reversible variable displacement-pump adapted to be driven in one direction or the other, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means tendin to adjust said pump to zero displacement, means responsive to said pump being driven in one direction or the other for adjusting said pump to cause it to discharge in the same direction and said motor to operate in only one direction regardless of the direction in which said pump is driven, and means operable only after the speed of said pump has reached a given value for varying pump displacement inversely to variations in pump speed above that value to thereby avoid corresponding variations in the speed of said motor.

11. In a hydraulic drive, the combination of a main pump adapted to be driven at varying speeds, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said main pump,

an auxiliary pump driven in unison with said main pump, hydraulic means operated by liquid supplied thereto by said auxiliary pump for moving said displacement varying means toward maximum displacement position, and hydraulic means responsive to the velocity of the liquid supplied by said auxiliary pump exceeding a predetermined rate for moving said displacement varyin means away from its maximum displacement position to thereby prevent an increase in the speed of said main pump above a predetermined speed from causing a corresponding increase in the speed of said motor.

12. In a hydraulic drive, the combination of a main pump adapted to be driven at varying speeds, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said main pump, means normally urging said displacement varying means to neutral position, an auxiliary pump driven in unison with said main pump, hydraulic means operated by liquid supplied thereto by said auxiliary pump for moving said displacement varying means toward maximum displacement position, and hydraulic means responsive to the 20 velocity of the liquid supplied by said auxiliary pump exceeding a predetermined rate for movin said displacement varying means away from its maximum displacement position to thereby prevent an increase in the speed of said main pump above a predetermined speed from causing a corresponding increase in the speed of said motor.

13. In a hydraulic drive, the combination of a main pump adapted to be driven at varying speeds, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said main pump, a flrst hydraulic actuator, a second hydraulic actuator, a floating lever pivoted to both of said actuators and connected to said displacement varying means, an auxiliary pump driven in unison with said main pump and adapted to deliver liquid to said first actuator and cause it to move said lever in a direction to effect movement of said displacement varying means toward maximum displacement position, means responsive to movement of said first actuator for directing liquid from said auxiliary pump to said second actuator, and means responsive to the velocity of the liquid delivered by said auxiliary pump exceeding a predetermined rate for causing said second actuator to move said lever in the opposite direction and thereby effect movement of said displacement varying means away from its maximum displacement position so as to prevent an increase in the speed of said main pump above a predetermined speed from causin a corresponding increase in the speed of said motor.

- 14. In a hydraulic drive, the combination of a main pump adapted to be driven at varying speeds, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, means for varying the displacement of said main pump, a first hydraulic actuator, a second hydraulic actuator, a floating lever pivoted to both of said actuators and connected to said displacement varying means, spring means normally urging said actuators to'such positions that said lever holds said displacement varying means in its neutral position, an auxiliary pump driven in unison with said main pump and adapted to deliver liquid to said first actuator and cause it to move said lever in a direction to effect movement of said displacement varying means toward maximum displacement position, means responsive to movement of said first actuator for directing liquid from said auxiliary pump to said second actuator, and means responsive to the velocity of the liquid delivered by said auxiliary pump exceeding a predetermined rate for causing said second actuator to move said lever in the opposite direction and thereby effect movement of said displacement varying means away from its maximum displacement position so as to prevent an increase in the speed of said main pump above a predetermined speed from causing a corresponding increase in the speed of said motor.

15. In a hydraulic drive, the combination of a main pump adapted to be driven in one direction or the other and provided with displacement varying means movable selectively in opposite directions from a neutral position, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, an auxiliary pump driven in one direction or the other in unison with said main pump and adapted to 21 deliver liquid in one direction or the other, and hydraulic means energized by said auxiliary pump and adapted to move said displacement varying means in one direction or the other in accordance with the direction of delivery of said auxiliary pump to thereby cause said main pump to discharge in a given direction and said motor to operate in only one direction regardless of the direction in which said main pump is driven.

16. In a hydraulic drive, the combination of a main pump adapted to be driven in one direction or the other at varying speeds and provided with displacement varying means movable selectively in opposite directions from a neutral position, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, an auxiliary pump driven in one direction or the other in unison with said main pump and adapted to deliver liquid in one direction or the other, hydraulic means energized by said auxiliary pump and adapted to move said displacement varying means in one direction or the other in accordance with the direction of delivery of said auxiliary pump to thereby cause said main pump to discharge in a given direction and said motor to operate in only one direction regardless of the direction in.which said main pump is driven, and means operable only after the speed of said main pump has reached a given value for causing said hydraulic means to vary pump displacement inversely to variations in pump speed above that value to thereby avoid corresponding variations in the speed of said motor.

17. In a hydraulic drive, the combination of a main pump adapted to be driven in one direction or the other at varying speeds and provided with displacement varying means movable selectively in opposite directions from a neutral position, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, a first hydraulic actuator, a second hydraulic actuator, means connectin both of said actuators to said displacement varying means so that operation of one or the other'of said actuators will cause said displacement varying means to be moved in one direction or the other, an auxiliary pump driven in one direction or the other in unison with said main pump and adapted to deliver liquid in one direction or the other, and means responsive to said auxiliary pump delivering liquid in one direction or the other for directing liquid from said auxiliary pump to that one of said actuators which will efiect movement of said displacement varying means in a direction to cause said main pump to discharge in a given direction and said motor to operate in only one direction regardless of the direction in which said main pump is driven.

18. In a hydraulic drive, the combination of a main pump adapted to be driven in one direction or the other at varying speeds and provided with displacement varying means movable selectively in opposite directions from a neutral position, a hydraulic motor, fluid channels connecting said pump and said motor to each other and forming therewith a hydraulic circuit, a first hydraulic actuator, a second hydraulic actuator, means connecting both of said actuators to said displacement varying means so that operation of one or the other of said actuators will cause said displacement varying means to be moved in one direction or the other, an auxiliary pump driven in one direction or the other in unison with said main pump and adapted to deliver liquid in one direction or the other, means responsive to said auxiliary pump delivering liquid in one direction or the other for directing liquid from said auxiliary pump to that one of said actuators which will eifect movement of said displacement varying means in a direction to cause said main pump to discharge in a given direction and said motor to operate in only one direction regardless of the direction in which said main pump is driven, and means responsive to the velocity of the' liquid delivered by said auxiliary pump exceeding a predetermined rate for causing said second actuator to effect movement of said displacement'varying means in the opposite direction so as to prevent an increase in the speed of said main pump above a predetermined speed from causing a corresponding increase in the speed of said motor.

19. In a hydraulic drive, the combination of a pump adapted to be driven in one direction or the other and having displacement varying means operable to reverse the direction of pump delivery in respect to the direction in which said pump is driven and also to vary the rate of pump 'delivery, a hydraulic motor, fluid channels connecting said pump to said motor and forming therewith a hydraulic circuit, and means responsive 'to a change in the direction in which said pump is driven for effecting operation of said displacement varyin means to cause said pump to deliver liquid to one side only of said motor so that said motor operates in one direction only regardless of the direction in which said pump is driven.

20. In a hydraulic drive, the combination of a pump adapted to be driven in one direction or the other and having displacement varying means operable to reverse the direction of pump delivery in respect to the-direction in which said pump is driven and also to vary the rate of pump delivery, a hydraulic motor, fluid channels connecting said pump to said motor and forming therewith a hydraulic circuit, means responsive to a change in the direction in which said pump is driven for efiecting operation of said displacement varyin means to cause said pump to deliver liquid to one side only of said motor so that said motor operates in one direction only regardless of the direction in which said pump is driven, and means responsive to variations in pump speed for effecting operation of said displacement varying means to vary pump displacement inversely to variations in pump speed and thereby avoid corresponding variations in the speed of said motor.

WALTER FERRI S.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Hanson Jan. 4, 1938 

